<template>
    <table class="zx-month-table" @click="handleMonthTableClick" @mousemove="handleMouseMove">
        <tbody>
            <tr v-for="(row, key) in rows" :key="key">
                <td v-for="(cell, key) in row" :key="key" :class="getCellStyle(cell)">
                    <div>
                        <a class="cell">{{ t('el.datepicker.months.' + months[cell.text]) }}</a>
                    </div>
                </td>
            </tr>
        </tbody>
    </table>
</template>

<script type="text/babel">
import Locale from '@src/mixins/locale';
import { isDate, range, getDayCountOfMonth, nextDate } from '@src/utils/date-util';
import { hasClass } from '@src/utils/dom';
import { arrayFindIndex, coerceTruthyValueToArray, arrayFind } from '@src/utils/util';

const datesInMonth = (year, month) => {
    const numOfDays = getDayCountOfMonth(year, month);
    const firstDay = new Date(year, month, 1);
    return range(numOfDays).map(n => nextDate(firstDay, n));
};

const clearDate = (date) => {
    return new Date(date.getFullYear(), date.getMonth());
};

const getMonthTimestamp = function (time) {
    if (typeof time === 'number' || typeof time === 'string') {
        return clearDate(new Date(time)).getTime();
    } else if (time instanceof Date) {
        return clearDate(time).getTime();
    } else {
        return NaN;
    }
};
export default {

    mixins: [Locale],
    props: {
        disabledDate: {},
        value: {},
        selectionMode: {
            default: 'month',
        },
        minDate: {},

        maxDate: {},
        defaultValue: {
            validator(val) {
                // null or valid Date Object
                return val === null || isDate(val) || (Array.isArray(val) && val.every(isDate));
            },
        },
        date: {},
        rangeState: {
            default() {
                return {
                    endDate: null,
                    selecting: false,
                };
            },
        },
    },

    data() {
        return {
            months: ['jan', 'feb', 'mar', 'apr', 'may', 'jun', 'jul', 'aug', 'sep', 'oct', 'nov', 'dec'],
            tableRows: [[], [], []],
            lastRow: null,
            lastColumn: null,
        };
    },

    computed: {
        rows() {
            // TODO: refactory rows / getCellClasses
            const rows = this.tableRows;
            const disabledDate = this.disabledDate;
            const selectedDate = [];
            const now = getMonthTimestamp(new Date());

            for (let i = 0; i < 3; i++) {
                const row = rows[i];
                for (let j = 0; j < 4; j++) {
                    let cell = row[j];
                    if (!cell) {
                        cell = { row: i, column: j, type: 'normal', inRange: false, start: false, end: false };
                    }

                    cell.type = 'normal';

                    const index = i * 4 + j;
                    const time = new Date(this.date.getFullYear(), index).getTime();
                    cell.inRange = time >= getMonthTimestamp(this.minDate) && time <= getMonthTimestamp(this.maxDate);
                    cell.start = this.minDate && time === getMonthTimestamp(this.minDate);
                    cell.end = this.maxDate && time === getMonthTimestamp(this.maxDate);
                    const isToday = time === now;

                    if (isToday) {
                        cell.type = 'today';
                    }
                    cell.text = index;
                    const cellDate = new Date(time);
                    cell.disabled = typeof disabledDate === 'function' && disabledDate(cellDate);
                    cell.selected = arrayFind(selectedDate, date => date.getTime() === cellDate.getTime());

                    this.$set(row, j, cell);
                }
            }
            return rows;
        },
    },

    watch: {
        'rangeState.endDate'(newVal) {
            this.markRange(this.minDate, newVal);
        },

        minDate(newVal, oldVal) {
            if (getMonthTimestamp(newVal) !== getMonthTimestamp(oldVal)) {
                this.markRange(this.minDate, this.maxDate);
            }
        },

        maxDate(newVal, oldVal) {
            if (getMonthTimestamp(newVal) !== getMonthTimestamp(oldVal)) {
                this.markRange(this.minDate, this.maxDate);
            }
        },
    },

    methods: {
        cellMatchesDate(cell, date) {
            const value = new Date(date);
            return this.date.getFullYear() === value.getFullYear() && Number(cell.text) === value.getMonth();
        },
        getCellStyle(cell) {
            const style = {};
            const year = this.date.getFullYear();
            const today = new Date();
            const month = cell.text;
            const defaultValue = this.defaultValue ? Array.isArray(this.defaultValue) ? this.defaultValue : [this.defaultValue] : [];
            style.disabled = typeof this.disabledDate === 'function'
                ? datesInMonth(year, month).every(this.disabledDate)
                : false;
            style.current = arrayFindIndex(coerceTruthyValueToArray(this.value), date => date.getFullYear() === year && date.getMonth() === month) >= 0;
            style.today = today.getFullYear() === year && today.getMonth() === month;
            style.default = defaultValue.some(date => this.cellMatchesDate(cell, date));

            if (cell.inRange) {
                style['in-range'] = true;

                if (cell.start) {
                    style['start-date'] = true;
                }

                if (cell.end) {
                    style['end-date'] = true;
                }
            }
            return style;
        },
        getMonthOfCell(month) {
            const year = this.date.getFullYear();
            return new Date(year, month, 1);
        },
        markRange(minDate, maxDate) {
            minDate = getMonthTimestamp(minDate);
            maxDate = getMonthTimestamp(maxDate) || minDate;
            [minDate, maxDate] = [Math.min(minDate, maxDate), Math.max(minDate, maxDate)];
            const rows = this.rows;
            for (let i = 0, k = rows.length; i < k; i++) {
                const row = rows[i];
                for (let j = 0, l = row.length; j < l; j++) {
                    const cell = row[j];
                    const index = i * 4 + j;
                    const time = new Date(this.date.getFullYear(), index).getTime();

                    cell.inRange = minDate && time >= minDate && time <= maxDate;
                    cell.start = minDate && time === minDate;
                    cell.end = maxDate && time === maxDate;
                }
            }
        },
        handleMouseMove(event) {
            if (!this.rangeState.selecting) return;

            let target = event.target;
            if (target.tagName === 'A') {
                target = target.parentNode.parentNode;
            }
            if (target.tagName === 'DIV') {
                target = target.parentNode;
            }
            if (target.tagName !== 'TD') return;

            const row = target.parentNode.rowIndex;
            const column = target.cellIndex;
            // can not select disabled date
            if (this.rows[row][column].disabled) return;

            // only update rangeState when mouse moves to a new cell
            // this avoids frequent Date object creation and improves performance
            if (row !== this.lastRow || column !== this.lastColumn) {
                this.lastRow = row;
                this.lastColumn = column;
                this.$emit('changerange', {
                    minDate: this.minDate,
                    maxDate: this.maxDate,
                    rangeState: {
                        selecting: true,
                        endDate: this.getMonthOfCell(row * 4 + column),
                    },
                });
            }
        },
        handleMonthTableClick(event) {
            let target = event.target;
            if (target.tagName === 'A') {
                target = target.parentNode.parentNode;
            }
            if (target.tagName === 'DIV') {
                target = target.parentNode;
            }
            if (target.tagName !== 'TD') return;
            if (hasClass(target, 'disabled')) return;
            const column = target.cellIndex;
            const row = target.parentNode.rowIndex;
            const month = row * 4 + column;
            const newDate = this.getMonthOfCell(month);
            if (this.selectionMode === 'range') {
                if (!this.rangeState.selecting) {
                    this.$emit('pick', { minDate: newDate, maxDate: null });
                    this.rangeState.selecting = true;
                } else {
                    if (newDate >= this.minDate) {
                        this.$emit('pick', { minDate: this.minDate, maxDate: newDate });
                    } else {
                        this.$emit('pick', { minDate: newDate, maxDate: this.minDate });
                    }
                    this.rangeState.selecting = false;
                }
            } else {
                this.$emit('pick', month);
            }
        },
    },
};
</script>
